Communication networks are undergoing a rapid evolution from circuit switched technologies, originally developed for voice communications, to packet switched technologies. The packet technologies were originally developed for data communications, but as speed has increased and the technologies have evolved, the packet networks have been able to provide generic transport for all forms of information (voice, video, multimedia, text, etc.). Next generation networks providing end-to-end packet transport, typically, based on Internet Protocol (IP) packets, are already being deployed in many areas.
IP Multi-media Subsystem (IMS) is a new service architecture developed for IP type packet switched networks for rapidly deploying new IP based multi-media services. Originally developed as an extension of GSM (Global System for Mobile) type wireless networking standards, the IMS paradigm has been extended to other types of wireless/mobile network technologies as well as landline networks, particularly for advanced digital cable television/telephone network deployments. The architecture has been in development in 3GPP and 3GPP2 for several years. The development of the major framework is largely completed or in the process of completion. Early IMS products are becoming available from various manufacturers for lab or field trials and deployment.
For commercial development of any communication network, lawful intercept (LI) capability is often a mandatory requirement in most countries/regions. In the US, lawful intercept is mandated by Communications Assist to Law Enforcement Agency (CALEA) law. To support this LI mandate in the context of the new IMS architecture, some standards work has been done in the area of lawful intercept, notably in 3rd Generation Partnership Project (3GPP), Technical Specification Group Services and System Aspects, 3G security, Handover Interface for Lawful Interception (LI), V7.6.0, September 2006; and PacketCable™ 2.0, Electronic Surveillance Intra-Network Specification, PKT-SP-ES-INF-I03-070925, Sep. 25, 2007.
In 3GPP, work on support of LI has primarily focused on the handover interface between an IMS service provider and a Law Enforcement Agency (LEA), as illustrated in the high-level block diagram of FIG. 5. This interface specifies the protocol messages between the service provider and the LEA. It, however, does not specify the protocol, messages, or format to be used to provision information identifying the targets of the LI from an LI administration function (also called LI Server, or LIS). Neither does the 3GPP specify aspects of how to intercept a call, such as intercept access points to be used for completed call scenarios, the protocols to be used to pass intercepted content to mediation functions, etc.
The recent PacketCable 2.0 standard cited above moves one step further by specifying not only the handover interface (The pkt-laes-1 interface), but also Intercept Access Points (IAPs), IMS internal network interfaces between IMS components (pkt-laees-3), and IMS components and LI delivery function (pkt-laes-2, pkt-laes-4, pkt-laes-5, and pkt-laes-6) as shown in FIG. 6. PacketCable 2.0 assumes that all Call Session Control Functions (CSCFs) are provisioned with lists of the LI targets, but it does not specify the interface between CSCFs and the LI administration function at the LIS (not shown in above diagram). The method and interface protocol are left open. Different methods could be used.
One straight-forward method of provisioning target information from the LIS would be to have the LIS interface directly with each CSCF, as shown in FIG. 7. In this method, the LIS provisions a complete list of LI targets onto each CSCF. The reason to have a complete list at each CSCF is because it is unknown prior to registration which CSCF will end up being assigned to serve a previously unregistered User Equipment (UE) device that will be a surveillance target for LI purposes. However, there are a few drawbacks with this approach.
First of all, there is no standard interface between the LI Server and a CSCF. Each CSCF vendor tends to design and implement their own proprietary interfaces. For a multi-vendor IMS service provider, this could mean implementation of different proprietary interfaces on the LIS for various CSCFs from different vendors. The cost of development and maintenance of LIS and CSCF interfaces would likely become significant.
Another major drawback is the number of interfaces with which each LIS has to manage. In a medium to large sized network, the number of CSCFs could become significant. Any addition or removal to CSCF would mean changes to LIS configuration and requires associated testing.
Hence a need exists for more effective techniques allowing a network operator/service provider to provision appropriate network elements with surveillance target related information, to allow the network to efficiently meet requirements for lawful intercept.